The invention herein described was made in the course of or under a contract thereunder with the United States Air Force Systems Command.
This invention relates to the hydrogenolysis of a saturated endo-endo dimer of norbornadiene, hereinafter referred to as HNN. Particularly the invention relates to the preparation of an isomeric pentacyclic liquid mixture from HNN.
The aforementioned isomeric liquid mixture can be used as a high energy missile fuel in either jet or rocket propulsion or as a diluent for other similar mixtures. Jet propulsion includes a jet engine which can be used for a missile, an aircraft and others and includes the three basic types, i.e. ramjet, turbojet and pulse jet. The term rocket generally refers to a device containing fuel incorporating its own oxygen or oxidizing agent.
Norbornadiene (bicyclo-(2.2.1)-2,5-heptadiene) can be prepared by reacting cyclopentadiene and acetylene at an elevated temperature, see U.S. Pat. No. 2,875,256 (Cl 260-666). Norbornadiene has the following structure: ##STR1## It can be dimerized into an olefinic endo-endo homo dimer having the following structure: ##STR2## Dimerization of norbornadiene to compound I is disclosed in "The stereochemical Course of Metal Catalyzed Cycloaddition Reactions of Norbornadiene", T. J. Katz et al, Tetrahedron Letters, No. 27, pp 2601-2605, 1967. The dimerization involves the use of a group VIII metal complex. Compound I is also disclosed in Chemical Abstracts, 91:1, Jan. 1, 1969, page 265, 87128q. The dimerization is also disclosed in "Dimerization and Trimerization of Norbornadiene by Soluble Rhodium Catalysts," Nancy Acton et al, Journal of the American Chemical Society, 94:15, July 26, 1972.
The olefinic bond in compound I can be hydrogenated. Generally a hydrogenation catalyst such as 5% rhodium-on-alumina is satisfactory. The temperature and pressure used for hydrogenation can be mild, e.g. about 125.degree. C. and 100 psig of hydrogen.
Hydrogenolysis of 3,3-dimethylnortricyclene and nortricyclene-3-spirocyclopropane using rhodium or platinum catalysts supported on pumice and palladium on silica is reported in J.C.S. Perkin II, 1976, pages 1412-1414, "Reactions over Metal Catalysts. Part II, Hydrogenolysis of 3,3-Dimethylnortricyclene and Nortricyclene-3-spirocyclopropane", M. N. Akhtar et al. Also use of transition metals, e.g. palladium for isomerization of cyclic hydrocarbons such as endo-endo-2,3-trimethylene is disclosed in Journal of Catalysts 26, 333-337, 1972, "Skeletal Rearrangement of Some Cyclic Hydrocarbons Catalyzed by Palladium," H. A. Quinn et al. Use of platinum or palladium with various supports in hydrogenolysis of certain cyclopropyl rings is reported in Journal of the American Chemical Society, 96:1, Jan. 9, 1974, "Hydrogenolysis of Substituted Nortricyclenes over Supported Metal Catalyst, "Methyl Migrations and Skeletal Rearrangements", M. N. Akhtar et al. In addition, use of supported platinum or palladium is compared with the use of platinum in acetic acid in the hydrogenolysis of certain norticyclenes in J.C.S. Chem. Comm, 1974, pages 155-156, "Unusual Alkyl Group Directing Effects During Cyclopropane Ring Hydrogenolysis," M. N. Akhtar et al.